Coated Metal Powders for Laser Powder Bed Fusion (L-PBF) Processing: A Review

Abstract

In the last years, functionalized powders are becoming of increasing interest in additive manufacturing (particularly in laser powder bed fusion processing, L-PBF), due to their improved flowability and enhanced processability, particularly in terms of laser absorbance. Functionalized powders may also provide higher final mechanical or physical properties in the manufactured parts, like an increased hardness, a higher tensile strength, and density levels close to theoretical. Coatings represent a possible interesting approach for powders’ functionalizing. Different coating methods have been studied in the past years, either mechanical or non-mechanical. This work aims to present an overview of the currently obtained coated powders, analyzing in detail the processes adopted for their production, the processability of the coated systems, and the mechanical and physical properties of the final parts obtained by using L-PBF for the powders processing.

Effect of Ultrafast Heating on Aisi 441 Ferritic Stainless Steel

“…Such results anyway also outlined the most important limitations of UFH process with respect to conventional steel-processing lines [8]. As a matter of fact, the increase in terms of heating rate strongly affects the phase transformation kinetics and as consequence steel mechanical properties: results reported in literature clearly show that an increase in terms of heating rate enhances the α/γ transformation temperature, with a refinement of the austenitic grain size [9][10][11][12]. At the same time, an increase in α/ transformation temperature [13] reduces the available carbon amount which can be dissolved in γ phase and this implies a reduction of the hardenability [14].…”

Bonding of Interface Bimetal Aluminum-Bronze for Bimetal Bushing Produced by Solid Liquid Method

“…Microstructure of a biphasic aluminum bronze alloy with equilibrium cooling contains of a light grain (α phasa) and a dark grain. This structure is resulted from the equilibrium transformation of β at rates lower than 10°C/min, which transformed by eutectoid reaction at 565°C into lamellar structure [25]. Table 3 shows the main compositions of each layer.…”

“…Aluminum bronzes with high Aluminum content will have large amounts of the fragile phase γ and would be unsuitable for industrial applications. Therefore Cu-Al alloys with contents higher than 12% wt Al are not used for manufacturing [25]. However, higher hardness does not necessarily result in better wear resistance.…”

Emerging Functional Metals in Additive Manufacturing

“…[47,48] The absorption of bulk copper increases from %5% with 1 μm IR laser to %60% with a green laser. [50] However, the absorption of pure copper powder has been reported to be much higher (30%-40% in the IR laser spectrum) depending on the particle size distribution (PSD). [48,49] Therefore, it is recommended that a laser beam with a power of minimum 300 W is used for a successful print job.…”